Certain businesses and services need to monitor the use of articles comprising their stock in trade. One obvious example is the need to monitor inventory of articles in a manufacturing environment, or in the chain of distribution from manufacture to disposition with the end user. Bar code use has become widespread for those applications, with articles or their packages bearing a visible bar-code label containing information identifying the product by such factors as model number, capacity, weight, or the like. An optical reader scans the visible bar code as desired, producing a signal which is decoded to reproduce the information previously encoded on the label. Various bar coding techniques and apparatus for reading bar codes are known to those skilled in the art.
A similar need to identify articles exists in fields other than manufacture and distribution. For example, in the rental and return of reusable articles, the need exists to identify each article and thereby create a history of use or other attributes in connection with that article. In some instances, optically-readable bar code labels can be affixed to the articles and read at various times, for example, when the article is delivered to a customer and later returned by the customer. However, the reliable operation of such bar-code labeling systems depend on a label or tag that remains visible throughout the expected lifetime of the article. This requirement makes the use of optical bar coding impracticable for applications where the encoded labels are likely to become disfigured or torn off in use.
One example of applications where optical bar coding is not feasible is the service of renting industrial mats. These mats typically are rented to customers of a mat-rental service, with the customer from time to time receiving fresh mats in place of ones that may have become soiled or worn. Mats removed from customer service are inspected for damage and wear, and are laundered for reuse with the same or other customers. Mats of any given kind and size are virtually identical and thus are indistinguishable from each other, making it difficult for the mat rental company to control its inventory of the mats. Moreover, these companies find it desirable to identify each mat with the date the mat was first put in service, the customer(s) for the mat, the service route and route driver responsible for the particular mat, the manufacturer of the mat, and other factors pertaining to the origin, durability, or rental history of the mat.
Optical bar coding has not met with favor in tagging industrial mats for identification. Bar-code labels can become damaged or removed from the mats during machine laundering, and the sometimes-harsh environments of use for such mats can disfigure or damage the labels. A proposed alternative to optical bar coding requires a radio-frequency (RF) tag attached to each mat, each tag being tuned or otherwise adapted to provide a unique electronic signature when subjected to an RF field. The costs associated with producing the required volume of uniquely-encoded RF tags and RF readers has inhibited widespread adoption of that tagging scheme.